With the development of information and communication technology, various wireless communication technologies have been developed. Among these technologies, a wireless local area network (WLAN) denotes technology for allowing wireless access to the Internet in homes, businesses or specific service areas using a mobile terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), a smart phone, or a tablet PC, based on radio frequency (RF) technology.
Standards for WLAN technology have been developed as Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards. WLAN technology conforming to the IEEE 802.11a standard is operated based on an orthogonal frequency division multiplexing (OFDM) scheme, and is capable of providing a maximum data rate of 54 Mbps in a 5 GHz band. WLAN technology conforming to the IEEE 802.11b standard is operated based on a direct sequence spread spectrum (DSSS) scheme, and is capable of providing a maximum data rate of 11 Mbps in a 2.4 GHz band. WLAN technology conforming to the IEEE 802.11g standard is operated based on the OFDM or DSSS scheme, and is capable of providing a maximum data rate of 54 Mbps in a 2.4 GHz band.
WLAN technology conforming to the IEEE 802.11n standard is operated based on the OFDM scheme in a 2.4 GHz band and a 5 GHz band, and is capable of providing a maximum data rate of 300 Mbps for four spatial streams when a Multiple-Input Multiple-Output OFDM (MIMO-OFDM) scheme is used. WLAN technology conforming to the IEEE 802.11n standard may support a channel bandwidth of up to 40 MHz and is capable of providing a maximum data rate of 600 Mbps in that case.
As the popularization of such WLAN technology has been activated and applications using WLANs have been diversified, the requirement for new WLAN technology that supports throughput higher than that of existing WLAN technology is increasing. Very high throughput (VHT) WLAN technology is proposed technology that supports a data rate of 1 Gbps or more. Meanwhile, in a system based on such WLAN technology, a problem arises in that, as the distance between WLAN devices increases, communication efficiency is deteriorated.